Polyurethanes prepared from polyether or polyester polyols, organic diisocyanates and polyethers having terminal hydroxyl and unsaturated groups, or terminal hydroxyl and pendant unsaturated groups, are soluble in solvents for deposition on a carrier that after removal of the solvent can be wound and processed as by calendaring and slitting immediately after removal from a solvent drying oven without layer to layer adhesion or other disruption of the coating. After such processing, the binder compositions containing the polyurethane may be crosslinked or cured by electron beam to provide a cross-linked polymer. These polyurethanes are useful in magnetic recording media wherein the magnetic coating contains a magnetic material, usually a ferri-magnetic material, embedded in a binder matrix of these polyurethanes and small amounts of other additives such as lubricants, dispersants, conductive agents and the like. However, these materials are limited by the amount of cross-linking or the degree of cure obtainable in electron beam cures. Systems having more flexibility are desired.
U.S. Pat. No. 4,255,243 discloses photo-crosslinkable unsaturated poly-(carbonate-urethanes) obtained by condensing a diisocyanate with a polycarbonate-diol and a lower hydroxyalkyl acrylate. U.S. Pat. No. 4,260,703 discloses radiation curable urethane-acrylates prepared by reacting an alkoxylate of an ester diol such as 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate with a diisocyanate, capped with a hydroxyalkyl acrylate such as hydroxyethyl acrylate. U.S. Pat. No. 4,264,752 discloses compositions formed by the reaction of a polycarbonate polyol, a polyisocyanate and a hydroxy acrylate monomer as hydroxyethyl acrylate that can be used as radiation curable coatings. Also U.S. Pat. No. 4,254,230 discloses actinic radiation-curable unsaturated polyetherester urethanes in the presence of air. These are complex polymers containing at least one unsaturated urethane oligomer, said oligomer comprising the reaction product of at least one unsaturated active hydrogen-containing compound, at least one polyisocyanate, and at least one polyetherester. The amount of said unsaturated compound being present in amount molar equivalent to the isocyanate compound. None of these compounds are completely satisfactory as polyurethanes for electron beam curing for magnetic tape applications.